|Publication number||US4961180 A|
|Application number||US 07/275,643|
|Publication date||Oct 2, 1990|
|Filing date||Nov 22, 1988|
|Priority date||Jul 20, 1985|
|Also published as||CA1275514C, DE3526020A1, EP0209946A2, EP0209946A3, US4947391|
|Publication number||07275643, 275643, US 4961180 A, US 4961180A, US-A-4961180, US4961180 A, US4961180A|
|Inventors||Dieter Schwarz, Hans-Dieter Kauschke|
|Original Assignee||U.S. Philips Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Non-Patent Citations (2), Referenced by (9), Classifications (9), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This is a continuation of application Ser. No. 887,581, filed July 18, 1986, abandoned.
1. Field of the Invention
The invention relates to an arrangement for producing information identifying non-occupied transmission paths in a digital transmission system. The transmission system is composed of a currently operating system for transmitting useful information in accordance with the time-division multiplex method, and a stand-by system.
2. Prior Art
The German "Auslegeschrift" DE-AS 27 53 420 discloses an arrangement for switching from operational to stand-by transmission paths in transmission systems for digital signals. In this known arrangement, predetermined bit positions in the time-division multiplex frame are used for identifying non-occupied transmission paths. However, these predetermined bit positions in the time-division multiplex frame signal are not available in every time-division multiplex transmission system. In the frame structure of a standardized 2 Mbit/s time-division multiplex systems, the frame alarm word and the system drawn word are alternatively transmitted in the first time slot of the frame. In the system alarm word, the bit positions 5 to 8 are freely available for the system user for transmitting additional information. Up to 16 different messages can be transmitted by means of these four bits that are commonly referred to as Y-message bits. In a standardized 8 Mbit/s and also in a standardized 34 Mbit/s time-division multiplex transmission system, such Y-message bits are not available. In a standardized 140 Mbit/s time-division multiplex transmission system, the frame structure comprises two Y-message bits in the bit positions 15 and 16 in set I (cf. for example TEKADE Technische Mitteilungen 1984, pages 17 to 22, more specifically page 17).
If the Y-message bits of the time-multiplex frame are used for the purpose of identifying non-occupied transmission paths, then this type of identification cannot be utilized for all types of time-division multiplex transmission systems, as such Y-message bits are not available in every frame structure (compare those of the 8 Mbit/s and 34 Mbit/s time-division multiplex transmission systems) or only a small number of different messages can be transmitted (in the 140 Mbit/s time-division multiplex transmission system having two Y-message bits, only four different messages can be transmitted).
In the arrangement disclosed in German "Auslegeschrift" DE-AS No. 27 53 420, the substitute switching from n currently operating systems to one stand-by system is effected by means of control arrangements included in the line terminal equipment of the stand-by system. The control arrangements always insert in the position of the Y-message bits an operational status character or, in the case of mal-functioning, the addresses of the currently operating system to be switched-over; the operating status character in the two transmission directions of the stand-by system can also be a standardized alarm-indication signal, commonly referred to as AIS.
The AIS is used in the digital transmission technique to report a transmission disturbance, for example a frame alignment disturbance (cf. the European Patent EP-Bl-0 031 943), and is a permanent-1 signal. According to European Patent, EP-Bl-0031943, this signal is produced by an AIS-generator arranged in the line terminal equipment and is used to suppress a subsequent alarm in the subsequent signal path. This prevents alarm signals from occurring in the entire down-stream section of the transmission path in the event of a disturbance in the upstream sections of the transmission path. From European Patent EP-Bl-0 031 943 it is known that it is also possible to include such AIS-generators in the intermediate regenerators (repeaters). In addition to the AIS generators, the line terminal equipment also includes supervision arrangements connected to a central monitoring station via a control line. The AIS-generator in question can be connected to the output of the line terminal equipment at the receiving side by means of a change-over switch that is remotely controlled by the central station. Furthermore, it is known from the above-mentioned publication (TEKADE Technische Mitteilungen 1984, pages 17 to 22) to provide in a plesiochronous digital signal multiplexer a supervision circuit at the interface. E 140 Mbit/s (SSTEE) for recognizing the AIS-signal in the sequence digital signal. On page 20 of said publication, it is set forth that for stand-by switching purposes a switch-over from the operational input B at the input of the SSTEE-interface to a second (stand-by) input E can be effected, which change-over action of the switch can be effected manually or automatically and be remotely controlled. Before the change-over action, no signal is transmitted through the stand-by channel in the 140-Mbit/s plane.
The invention has for its object to provide an arrangement for producing an information identifying non-occupied transmission paths in a digital transmission system which can be used for identifying a ready-for-operation status of digital signal links having any frame structure whatsoever and any bit rate whatsoever.
This object is accomplished by means of an arrangement of the type set forth in the field of the invention which produces a signal pattern which is: periodic, distributed over the time-division multiplex frame and is not simulated by frame alignment or system alarm words, nor by the useful information.
The arrangement according to the invention has the advantage that the arrangements already present in existing time-division multiplex transmission systems for producing the alarm-indication-signal AIS can also be used for producing the digital signal pattern and consequently the additional circuit efforts are small. The digital signal pattern can be used irrespective of the frame structure opted for and does not cause any restriction in the data-transparency. Compared to the identification of the non-occupied transmission path by means of Y-message bits as described in German "Auslegeschrift" DE-AS No. 27 53 420, the distribution of the digital signal pattern over the time-division multiplex frames also simplifies the recognition of the information identifying a non-occupied transmission path.
If the digital signal pattern is produced by inverting the standardized AIS then it is, for example, only necessary to add an inverter to the AIS-generator described in European Patent EP-Bl-0 031 943.
Also in the arrangement for recognizing the information identifying non-occupied transmission paths resolving the digital signal pattern down to the bit plane is not necessary, contrary to the arrangement described in the German "Auslegeschrift" DE-AS 27 53 420. With the arrangement according to the invention it is not only possible to recognize the digital signal pattern, but moreover also the standardized AIS can be recognized. The circuit effort for the arrangement is low and commercially available digital logic circuits can be used for the circuitry.
The invention and how it can be put into effect will now be described in greater detail by way of example with reference to an embodiment shown in the accompanying drawing, in which:
FIG. 1 shows the network structure of the digital transmission system;
FIG. 2 shows the arrangement according to the invention for recognizing the information identifying non-occupied transmission paths of a time-division multiplex transmission system employing CMI-encoding; and
FIG. 3 shows the variation versus time of the signals produced in the arrangement of FIG. 2.
FIG. 1 shows a possible section of the network of a time-division multiplex transmission system. Combining the digital signals for obtaining a PCM transmission system (from basic PCM 30 systems (primary blocks composed of 30 PCM channels) by means of digital signal multiplexers is not illustrated in FIG. 1. The information stream occurring at the output of a plesiochronous digital signal multiplexer is respectively applied to the digital-signal standby-switch circuits DSE-A, DSE-B, DSE-D and DSE-C shown in FIG. 1. The information identifying non-occupied transmission paths is produced by arrangements provided in the digital-signal stand-by-switch circuits DSE-A to DSE-D or in the line terminal equipment LE. In addition to the arrangement for producing a digital signal pattern MDS, these arrangements include an arrangement for recognizing the digital signal pattern MDS (cf. FIG. 2).
When the non-occupied transmission paths are standby paths which are reserved for the case of disturbance, a switch-over from the disturbed operating path to a standby-path in the digital-signal stand-by-switch circuits DSE-A to DSE-D can be effected. Using a digital signal pattern MDS which is a periodic signal and is distributed over the time-division multiplex frame in a time-division multiplex transmission system, has the advantage that for recognizing the information it is not necessary to resolve the frame down to the bit plane and consequently non-occupied transmission paths of any digital transmission paths of any digital transmission systems can be characterized in a simple way. If the inverted version of the standardized alarm-indication-signal AIS is used as the digital signal pattern MDS, then only minor changes are required both in existing and commercially available AIS-generators and in AIS-recognition circuit. Hereinafter the method of switching to the stand-by circuits will be described in greater detail, on the basis of the possible different modes of operation. Switching to a stand-by path ES between the locations A, B, C and D can be effected manually, semi-automatically or fully automatically. When switching is effected manually, the operators decide (a telephone connection existing between the different locations) the instant at which the change-over will be made and to which one of the stand-by paths ES. For semi-automatic switching, the change-over is effected through a supervisory link UV by means of a control arrangement in a higher-ranking exchange and it is triggered by pushing a button. For fully automatic switching, the central control refers to the instantaneous network mapping, chooses a free stand-by path and switches to this free stand-by path ES.
When the operating path BS is in good order, a respective valid digital signal GDS is received and transmitted in the corresponding arrangements (line terminal equipment LE or digital-signal stand-by-switch circuits DSE-A to DSE-D). For instance, when the path BS between the locations A and B is in proper working order, a valid digital signal GDS is transmitted from location A and received in location B. From there, a valid digital signal GDS is also transmitted through the path BS in the return direction to location A and received there. Through the stand-by path ES, shown in FIG. 1, between the locations A and B the digital signal pattern MDS is transmitted from location A (or location B) and received at location B (or location A). This also holds for the stand-by paths ES between the locations A and B, D and C as well as B and C. Receiving the digital signal pattern MDS at the ends of a stand-by path ES (between the locations A and B, B and C, A and D, D and C) means that the corresponding stand-by path ES is in proper working order.
When the path BS from location A to location B is disturbed, and not disturbed from location B to location A, a valid digital signal GDS is transmitted from location A. In location B no digital signal KDS or AIS is received. KDS then implies an interruption between line terminal equipment LE in question and digital-signal stand-by-switch circuit DSE-B and AIS implies an interruption between line terminal equipment LE. Since, as assumed above, the path BS between the location B and the location A is in good order, a valid digital signal GDS is transmitted from the location B and received in location A. Assuming that the stand-by path ES between the location A and the location B is in proper working order and is free (i.e. the digital signal pattern MDS is received both in location A and in location B), a change-over to this stand-by path ES can be effected. After switching, the digital signal pattern MDS is transmitted from location A through the path BS, and furthermore KDS or AIS is received in the location B. The digital signal pattern MDS is transmitted from location B and is received in location A. After switching to this stand-by path ES between location A and location B, the respective valid digital signal GDS transmitted through this stand-by path ES is received again in location A and in location B.
When the path BS between location A and location B has been restored, the digital signal pattern MDS transmitted from location A through the path BS is received again in location B, so that a switch from the stand-by path ES to the path BS between the locations A and B can be effected. After the switching action, the valid digital signal GDS is again transmitted through the path BS and the digital signal pattern MDS is again transmitted through the stand-by path ES.
For the following discussion, it is assumed that the operating path BS and the stand-by path ES between the location A and the location B are disturbed. The valid digital signal GDS transmitted through the path BS from location A and the digital signal pattern MDS transmitted through the stand-by path ES are not received in location B, but in location B the signals KDS or AIS are recognized. A switch to the stand-by path ES between location A and location D and also to the stand-by path ES between location D and C can be effected when both stand-by paths ES are in proper working order, that is to say when the digital signal pattern MDS is received in both location A and location D as well as in location C. After the switch to the respective stand-by paths ES between location A and location D and between location D and location C, the digital signal pattern MDS is again exchanged between the locations A and B, B and C through the operating paths BS now switched to the stand-by mode. After the disturbance in the operating path BS between the location A and location B has been eliminated and the subsequent switch-back to the normal mode, the digital signal pattern MDS is again transmitted through the stand-by paths ES between location A and location B and also between location D and location C and the valid digital signal GDS is transmitted and received through the respective paths BS between the locations A and B and between the locations B and C.
FIG. 2 shows an embodiment of an arrangement for recognizing the information identifying non-occupied transmission paths. The arrangement comprises two D flip-flops whose Q-outputs are connected to the two inputs of an EXCLUSIVE-OR gate EG. The digital signal ES received in the relevant equipment, for example the line terminal equipment LE, is applied to the respective preparatory input D of the two D flip-flops D1 and D2. The operating clock BT is applied to the clock input of the first D flip-flop D1 and the inverted operating clock BT is applied to the clock input of the second D flip-flop. The signals produced at the output A of the EXCLUSIVE-OR-gate EG obtained in response to the digital signal applied to the preparatory input D will now be described in greater detail with reference to FIG. 3.
If a valid digital signal GDS is applied to the preparatory input D of the two D flip-flops D1 and D2, then a non-periodical digital signal is produced at the output A of the EXCLUSIVE OR gate EG. If in contrast therewith the alarm-indication-signal AIS is applied to the preparatory input D, then the operational clock BT is produced at the output A. If the digital signal pattern MDS is applied to the preparatory input D, then the signal at the output A assumes the binary "1" state. If, finally, no valid digital signal KDS is applied to the preparatory input D, then the binary "0" state occurs at the output A. In each of these cases, noise impulses may be present in practice.
The method according to the invention for identifying non-occupied transmission paths now provides the possibility to distinguish between the situation in which the individual transmission path is not occupied and in proper working order and the situation in which a line interruption occurs.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3715503 *||Feb 16, 1971||Feb 6, 1973||Stromberg Carlson Corp||Automatic transfer arrangement for telephone system|
|US4365247 *||Jan 7, 1981||Dec 21, 1982||Societe Anonyme De Telecommunications||End station digital transmission link relieving system|
|US4365248 *||Jan 7, 1981||Dec 21, 1982||Societe Anonyme De Telecommunications||Digital transmission link relief triggering system|
|US4393493 *||Nov 10, 1980||Jul 12, 1983||International Telephone And Telegraph Corporation||Automatic protection apparatus for span lines employed in high speed digital systems|
|US4513411 *||Sep 1, 1982||Apr 23, 1985||At&T Bell Laboratories||Transmission of status report of equipment in a digital transmission network|
|US4550403 *||Mar 29, 1983||Oct 29, 1985||Societe Anonyme De Telecommunications||Method for transmitting a HDBn code signal with an auxiliary binary signal in a digital transmission line and system for monitoring repeaters in the line by means of auxiliary signals|
|EP0031943A1 *||Dec 22, 1980||Jul 15, 1981||Siemens Aktiengesellschaft||Control of transmission lines for digital signals|
|GB2012526A *||Title not available|
|1||W. Fischer et al., "DSMX 34/140-Ein Plesiochroner Digitalsignal-Multiplexer", Tekade Tech. Mitt., 1984, pp. 17-22.|
|2||*||W. Fischer et al., DSMX 34/140 Ein Plesiochroner Digitalsignal Multiplexer , Tekade Tech. Mitt., 1984, pp. 17 22.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US5125082 *||Jun 16, 1989||Jun 23, 1992||Nec Corporation||Management system capable of quickly assigning a terminal endpoint identifier to a terminal equipment unit|
|US5187705 *||Jan 16, 1991||Feb 16, 1993||Kabushiki Kaisha Toshiba||Data error detecting apparatus for key telephone system and the detecting method therefor|
|US5265096 *||Jul 3, 1991||Nov 23, 1993||Transwitch Corporation||Sonet alarm indication signal transmission method and apparatus|
|US5319631 *||Jan 11, 1993||Jun 7, 1994||Siemens Aktiengesellschaft||Method for measuring in the subscriber area of an integrated services digital network system|
|US5321688 *||Nov 14, 1991||Jun 14, 1994||Hitachi, Ltd.||Method and apparatus for transmission of failure information of virtual path in ATM network|
|US6038662 *||Feb 12, 1998||Mar 14, 2000||Powerchip Semiconductor Corp.||Bubble evaporation circuit for eliminating bubble errors in thermal code and its method|
|US6055226 *||Aug 8, 1997||Apr 25, 2000||Alcatel||Method to signal a failure in a mixed PDH/SDH network in order to enable the latter to provide a service such as a protection mechanism|
|US6339585 *||May 5, 1998||Jan 15, 2002||Philips Electronics North America Corp.||Error-recovery mechanism using a temporary forwarder in a wireless-ATM network|
|US6442133 *||May 23, 2001||Aug 27, 2002||Nec Corporation||Switchboard having a dual switching system|
|U.S. Classification||370/227, 370/522|
|International Classification||H04J3/14, H04J3/12, H04B1/74|
|Cooperative Classification||H04J3/12, H04B1/74|
|European Classification||H04J3/12, H04B1/74|
|Mar 31, 1994||FPAY||Fee payment|
Year of fee payment: 4
|Apr 8, 1996||AS||Assignment|
Owner name: LUCENT TECHNOLOGIES INC., NEW JERSEY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:U.S. PHILIPS CORPORATION;REEL/FRAME:007854/0516
Effective date: 19960403
Owner name: LUCENT TECHNOLOGIES INC., NEW JERSEY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:U.S. PHILIPS CORPORATION;REEL/FRAME:007881/0513
Effective date: 19960403
|Mar 13, 1998||FPAY||Fee payment|
Year of fee payment: 8
|Mar 28, 2002||FPAY||Fee payment|
Year of fee payment: 12